The present invention relates to a shielded multi-core cable in which a plurality of insulator rods each having embedded therein one of a plurality of conductive cores, are tightly received in a cylindrical shielding conductive pipe so that the conductive cores are ;held therein around the center axis thereof, and the invention also pertains to a method of making such a shielded multi-core cable.
A conventional shielded multi-core cable and its manufacturing method will be described with reference to FIGS. 21 through 24; the manufacturing method involves a sequence of steps described below.
The manufacture begins with the preparation of an insulator-covered wire G which has plural, for example, two conductive cores A1 and A2 circular in cross-section, for instance, and embedded side by side in a cylindrical insulator rod F at equal angles around the center axis thereof (FIGS. 21A and B), and a cylindrical conductive pipe E which has an inner diameter xcfx86E1 nearly equal to or larger than the outer diameter xcfx86F2 of the insulator rod F (FIGS. 21C and D).
Then, the insulator-covered wire G is inserted into the conductive pipe E (FIGS. 22A and B).
For the sake of brevity, the conductive pipe E is shown to have an inner diameter xcfx86E1 substantially equal to the outer diameter xcfx86F2 of the insulator rod F of the insulator-covered wire G.
Next, the conductive pipe E having inserted therein the insulator-covered wire G is subjected to drawing by means of a drawing die K (FIGS. 23A and B) having a circularly-sectioned through hole H whose inner diameter xcfx86H gradually varies lengthwise thereof from one end having an inner diameter xcfx86H1 nearly equal to or larger than the outer diameter xcfx86E2 of the conductive pipe E to the other end having an inner diameter xcfx86H2 smaller than the outer diameter xcfx86E2 of the conductive pipe E. That is, the conductive pipe E is drawn through the through hole H of the drawing die K from the one end of the larger inner diameter xcfx86H1 to the other end of the smaller inner diameter xcfx86H2 (FIG. 23A). By this, a conventional shielded multi-core cable M is obtained which has a construction in which two conductive cores A1xe2x80x2 and A2xe2x80x2, embedded side by side in a cylindrical insulator rod Fxe2x80x2 tightly fitted in and held integrally with a cylindrical shielding conductive pipe Exe2x80x2, lie in juxtaposition to each other in the shielding conductive pipe Exe2x80x2 which has an outer diameter xcfx86H2xe2x80x2 equal to the smaller inner diameter xcfx86H2 of the through hole H of the drawing die K (FIGS. 24A and B).
In this instance, since the inner diameter xcfx86E1xe2x80x2 of the shielding conductive pipe Exe2x80x2 of the shielded multi-core cable M is smaller than the inner diameter xcfx86E1 of the conductive pipe E, the insulating material forming the insulator rod F of the insulator-covered wire G is forced out of the shielding conductive pipe Exe2x80x2 of the shielded multi-core cable M. The excess insulating material is removed after the drawing step.
The conventional shielded multi-core cable M (FIGS. 24A and B), fabricated by the method depicted in FIGS. 21 through 24, is commonly used after being subjected to an end treatment as depicted in FIG. 25. One end portion of the shielding conductive pipe Exe2x80x2 is peeled off to expose one end portion of the insulator rod Fxe2x80x2, and the exposed end portion of the latter is partly removed to expose the two conductive cores A1xe2x80x2 and A2xe2x80x2 at one end thereof. Occasionally the situation arises where it is desirable that the free end portion of the two conductive cores A1xe2x80x2 and A2xe2x80x2 be widely spaced apart.
Since the two conductive cores A1xe2x80x2 and A2xe2x80x2 are embedded side by side in the common insulator rod Fxe2x80x2, however, there is no choice but to gradually open up the space between the two cores A1xe2x80x2 and A2xe2x80x2 from the free end position of the insulator rod Fxe2x80x2 toward their free ends by making a cut in the insulator rod Fxe2x80x2 between the two conductive cores A1xe2x80x2 and A2xe2x80x2 ftom the free end of the rod Fxe2x80x2 to that of the shielding conductive pipe Exe2x80x2.
Accordingly, when it is required that the free ends of the two conductive cores A1xe2x80x2 and A2xe2x80x2 be widely spaced apart in practical use, it is impossible to meet the requirement without elongating the exposed free end portions of the two conductive cores A1xe2x80x2 and A2xe2x80x2 in the abovementioned end treatment or making a cut in the insulator rod Fxe2x80x2 from the free end thereof toward that of the shielding conductive pipe Exe2x80x2 between the conductive cores A1xe2x80x2 and A2xe2x80x2 after the end treatment.
Thus, the conventional shielded multi-core cable M depicted in FIG. 24 has a shortcoming that the space between the free ends of the two conductive cores A1xe2x80x2 and A2xe2x80x2 cannot be opened up in the practical use after the end treatment without making a cut in the insulator rod Fxe2x80x2 from the free end thereof toward that of the shielding conductive pipe Exe2x80x2 or increasing the lengths of the exposed free end portions of the conductive cores A1xe2x80x2 and A2xe2x80x2.
Furthermore, according to the conventional shielded multi-core cable fabricating method shown in FIGS. 21 through 24, if it is possible to obtain, in the step of its preparation (FIGS. 21A and B), the insulator-covered wire G of a construction in which the two conductive cores A1 and A2 embedded side by side in the insulator rod F are exactly symmetrical over the entire length thereof in respect of the plane containing the center axis of the insulator rod F (that is, the conductive cores A1 and A2 are embedded in the insulator rod F so that, in any plane orthogonal to the center axis of the insulator rod F, the line joining the centers of the conductive cores A1 and A2 passes through the center of the insulator rod F and the conductive cores A1 and A2 are both exactly symmetrical with respect to the center of the insulator rod F), the shielded multi-core cable M can be obtained which has the construction wherein the two conductive cores A1xe2x80x2 and A2xe2x80x2 embedded side by side in the insulator rod Fxe2x80x2 are exactly symmetrical over the entire length thereof in respect of the plane containing the center axis of the insulator rod Fxe2x80x2 (that is, the conductive cores A1xe2x80x2 and A2xe2x80x2 are embedded in the insulator rod F so that, in any plane orthogonal to the center axis of the insulator rod Fxe2x80x2, the line joining the centers of the conductive cores A1xe2x80x2 and A2xe2x80x2 passes through the center of the insulator rod Fxe2x80x2 and the conductive cores A1xe2x80x2 and A2xe2x80x2 are both exactly symmetrical with respect to the center of the insulator rod Fxe2x80x2).
In practice, however, since the two conductive cores A1 and A2 are both disposed at positions off the center axis of the insulator rod F, it is difficult to prepare the insulator-covered wire G of the abovementioned construction in which the two conductive cores A1 and A2 embedded side by side in the insulator rod F are exactly symmetrical over the entire length thereof in respect of the plane containing the center axis of the insulator rod F (that is. the conductive cores A1 and A2 are embedded in the insulator rod F so that, in any plane orthogonal to the center axis of the insulator rod F, the line joining the centers of the conductive cores A1 and A2 passes through the center of the insulator rod F and the conductive cores A1 and A2 are both exactly symmetrical with respect to the center of the insulator rod F).
On this account, difficultly is encountered in producing, by the step of drawing the conductive pipe E with the insulator-covered wire G inserted therein, the shielded multi-core cable M in which the two conductive cores A1xe2x80x2 and A2xe2x80x2 embedded side by side in the insulator rod Fxe2x80x2 are exactly symmetrical over the entire length thereof in respect of the plane containing the center axis of the insulator rod Fxe2x80x2 (that is, the conductive cores A1xe2x80x2 and A2xe2x80x2 are embedded in the insulator rod F so that, in any plane orthogonal to the center axis of the insulator rod Fxe2x80x2, the line joining the centers of the conductive cores A1xe2x80x2 and A2xe2x80x2 passes through the center of the insulator rod Fxe2x80x2 and the conductive cores A1xe2x80x2 and A2xe2x80x2 are both exactly symmetrical with respect to the center of the insulator rod Fxe2x80x2).
For the reasons given above, the conventional shielded multi-core cable manufacturing method depicted in FIGS. 21 through 24 has a defect that intended excellent high-frequency characteristics cannot easily be achieved for the shielded multi-core cable M.
Furthermore, as is evident from the above, according to the conventional shielded multi-core cable manufacturing method shown in FIGS. 21 through 24, since the two conductive cores A1xe2x80x2 and A2xe2x80x2 are embedded side by side in the common insulator rod Fxe2x80x2, the free ends of the conductive cores A1xe2x80x2 and A2xe2x80x2 can be widely spaced apart only by making a cut in the insulator rod Fxe2x80x2 from the free end thereof to that of the shielding conductive pipe or lengthening the exposed free end portions of the cores.
Accordingly, an object of the present invention is to provide a novel shielded multi-core cable and its manufacturing method which are free from the abovementioned detects.
Another object of the present invention is to provide a novel shielded multi-core cable of a construction in which the free ends of one and the other conductive cores can be widely spaced apart without lengthening their exposed free end portions.
Still another object of the present invention is to provide a novel shielded multi-core cable manufacturing method which allows ease in manufacturing a shielded multi-core cable with excellent high-frequency characteristics.
A shielded multi-core cable according to an aspect of the present invention has a construction in which a plurality n of insulator rods, each having embedded therein one of a plurality n of conductive cores, are tightly received in a cylindrical shielding conductive pipe so that said plurality n of conductive cores are held therein about the center axis thereof.
A shielded multi-core cable according to another aspect of the present invention has a construction in which a plurality n of first insulator rods, each having embedded therein one of a plurality n of conductive cores, and a plurality n of second insulator rods are tightly received in a cylindrical shielding conductive pipe alternately about the enter axis thereof so that said plurality n of conductive cores are held therein about the center axis thereof.
A shielded multi-core cable according to another aspect of the present invention has a construction in which a cylindrical insulating tube and a plurality n of insulator rods, each having embedded therein one of a plurality n of conductive cores and tightly received in said cylindrical insulating tube about the center axis thereof are tightly received in a cylindrical shielding conductive pipe so that said plurality n of conductive cores are held therein about the center axis thereof.
A shielded multi-core cable according to another aspect of the present invention has a construction in which a cylindrical insulating tube, a plurality n of first insulator rods, each having embedded therein one of a plurality n of conductive cores, and a plurality n of second insulator rods (said plurality n of first insulator rods and said plurality n of second insulator rods being tightly received in said cylindrical insulating tube alternately about the center axis thereof) are tightly received in a cylindrical shielding conductive pipe so that said plurality n of conductive cores are held therein about the center axis thereof.
A shielded multi-core cable manufacturing method according to aspect of the present invention comprises the steps of: (1) preparing a plurality n of insulator-covered wires each having a conductive core embedded in a cylindrical insulator rod concentrically therewith, and a cylindrical conductive pipe having an inner diameter large enough to receive said plurality n of insulator-covered wires; (2) inserting said plurality n of insulator-covered wires into said cylindrical conductive pipe around the center axis thereof; and (3) drawing said cylindrical conductive pipe with said plurality n of insulator-covered wires inserted therein, thereby obtaining a shielded multi-core cable of a construction in which a plurality n of insulator rods, formed by said cylindrical insulator rods of said plurality n of insulator-covered wires and each having embedded therein one of a plurality of conductive cores formed by said conductive cores of said plurality n of insulator-covered cores, are tightly received in a cylindrical shielding conductive about the center axis thereof so that said plurality n of conductive cores are held therein around the center axis thereof, said cylindrical shielding conductive pipe being formed by said cylindrical conductive pipe and having inner and outer diameter smaller than the latter.
A shielded multi-core cable manufacturing method according to another aspect of the present invention comprises the steps of: (1) preparing a plurality n of insulator-covered wires each having a conductive core embedded in a first cylindrical insulator rod concentrically therewith, a plurality n of second cylindrical insulator rods and a cylindrical conductive pipe having an inner diameter large enough to receive said plurality n of insulator-covered wires and said plurality n of second cylindrical insulator rods; (2) inserting said plurality n of insulator-covered wires and said plurality n of second cylindrical insulator rods into said cylindrical conductive pipe alternately around the center axis thereof; and (3) drawing said cylindrical conductive pipe with said plurality n of insulator-covered wires and said plurality n of second cylindrical insulator rods inserted therein, thereby obtaining a shielded multi-core cable of a construction in which a plurality n of first insulator rods, formed by said first cylindrical insulator rods of said plurality n of insulator-covered wires and each having embedded therein one of a plurality n of conductive cores, formed by said conductive cores of said plurality n of insulator-covered wires, and a plurality n of second insulator rods, formed by said plurality n of second cylindrical insulator rods, are tightly received in a cylindrical shielding conductive pipe so that said plurality n of conductive cores are held therein around the center axis thereof, said cylindrical shielding conductive pipe being formed by said cylindrical conductive pipe and having inner and outer diameters smaller than those of the latter.
A shielded multi-core cable manufacturing method according to another aspect of the present invention comprises the steps of: (1) preparing a plurality n of insulator-covered wires each having a conductive core embedded in a first cylindrical insulator rod concentrically therewith a cylindrical insulating tube having an inner diameter large enough to receive said plurality n of insulator-covered wires, and a cylindrical conductive pipe having an inner diameter large enough to receive said cylindrical insulating tube; (2) inserting said plurality n of insulator-covered wires and said cylindrical insulating tube into said cylindrical conductive pipe so that said cylindrical insulating tube is concentric therewith and receives said plurality n of insulator-covered wires arranged around the center axis thereof; and (3) drawing said cylindrical conductive pipe with said plurality n of insulator-covered wires and said cylindrical insulating tube inserted therein, thereby obtaining a shielded multi-core cable of a construction in which a cylindrical insulating tube, formed by said cylindrical insulating tube, and a plurality n of insulator rods, formed by said first cylindrical insulator rods of said plurality n of insulator-covered wires, each having embedded therein one of a plurality n of conductive cores formed by said plurality n of conductive cores and tightly received in said cylindrical insulating tube about the center axis thereof, are tightly received in a cylindrical shielding conductive pipe so that said plurality n of conductive cores are held therein about the center axis thereof, said cylindrical shielding conductive pipe being formed by said cylindrical conductive pipe and having inner and outer diameters smaller than those of the latter.
A shielded multi-core cable manufacturing method according to still another aspect of the present invention comprises the steps of: (1) preparing a plurality n of insulator-covered wires each having a conductive core embedded in a first cylindrical insulator rod concentrically therewith, a plurality n of second cylindrical insulator rods, a cylindrical insulating tube having an inner diameter large enough to receive said plurality n of insulator-covered wires and said plurality n of cylindrical insulator rods, and a cylindrical conductive pipe having an inner diameter large enough to receive said cylindrical insulating tube; (2) inserting said plurality n of insulator-covered wires, said plurality n of second cylindrical insulator rods and said cylindrical insulating tube into said cylindrical conductive pipe so that said cylindrical insulating tube receives said plurality n of insulator-covered wires and said plurality n of second cylindrical insulator rods alternately arranged around the center axis thereof; and (3) drawing said cylindrical conductive pipe with said plurality n of insulator-covered wires, said plurality n of cylindrical insulator rods and said cylindrical insulating tube inserted therein, thereby obtaining a shielded multi-core cable of a construction in which a cylindrical insulating tube, formed by said cylindrical insulating tube, a plurality n of first insulator rods formed by said first cylindrical insulator rods of said plurality n of insulator-covered wires and each having embedded therein one of a plurality n of conductive cores formed by said plurality n of conductive cores, and a plurality n of insulator rods formed by said plurality n of second cylindrical insulator rods (said plurality n of first insulator rods and said plurality n of second insulator rods being tightly received in said cylindrical insulating tube alternately about the center axis thereof) are tightly received in a cylindrical shielding conductive pipe so that said plurality n of conductive cores are held therein about the center axis thereof, said cylindrical shielding conductive pipe being formed by said cylindrical conductive pipe and having inner and outer diameters smaller than those of the latter.